The effect of air pollution on human health is a topic of considerable importance to scientists and policymakers. The existing literature on the health effects of air pollution focuses largely on premature mortality and hospital admissions as markers of health. The proposed research will provide the first large-scale evidence on how air and particularly ozone pollution affect medication purchases, and then it will demonstrate an application of this evidence by quantifying pollution-related medications as a hitherto unmeasured cost of climate change. Medications represent ten percent of total U.S. health expenditures, half the total cost of asthma, and an important means to decrease respiratory mortality. Additionally, air pollution may worsen health without causing hospital admissions or premature mortality. Yet nearly none of the scientific or policy literature assesses how Americans use medications to mitigate the health effects of air pollution. As a consequence it is likely that previous research has understated the public health costs of air pollution. Since the Environmental Protection Agency is currently evaluating the possibility of increasing regulations on ozone pollution, this type of evidence can play a central role in that decision. Specifically, this study will pursue four goals: (1) Produce large-scale evidence on the relationship between exposure to air pollution and the purchase of respiratory and other medications;(2) Leverage quasi-experimental variation in exposure to air pollution caused by the nonattainment rules in the Clean Air Act to isolate the causal effect of air pollution on medication purchases;(3) Integrate the econometric and epidemiological approaches to measuring the effect of air pollution on health;and (4) Assess the pollution medication-related costs of climate change. To achieve these goals, the study is compiling an unparalleled new dataset with two independent records of medication purchases, and controls for economics, demographics, regulations, copollutants, and weather, including aeroallergens. PUBLIC HEALTH RELEVANCE: Existing research on the health effects of air pollution focuses largely on premature mortality and hospitalizations as markers of health. This research proposes to use comprehensive data on medication prescriptions as a new approach to measuring the health impacts of exposure to air pollution. This focus on medications is particularly relevant for widespread but 'low-level'health consequences of air pollution that do not lead to premature mortality. In addition, medications are important since they represent a large share of the total cost of treating respiratory conditions such as asthma.